1. Field of the Invention
This invention generally relates to television signal distribution systems, and more particularly, to remote terminals or converters for use in connection with such systems.
2. Description of the Prior Art
Modern CATV systems employ in-house converters which can accept and process digital data emanating from a computer in a CATV head end. This digital data conveys commands which can enable/disable a converter, control the availability for viewing of channels and implement other ancillary functions as well. A CATV system in which a computer (Addressing Computer) can transmit commands to converters and the converters cannot return data to the computer is called a one-way addressable system.
Addressable CATV converters store digital data in an internal memory which defines the converter address and level of service to be provided to the subscriber.
Existing converters have a number of disadvantages. Establishing an address for the converter is a time consuming and expensive procedure to the manufacturer of the converter and/or the cable operator. Two basic approaches have been used. One approach is for the manufacturer of the converter to program data into non-volatile memory to store converter addresses. Another approach is for the manufacturer to ship converters to cable operators in a "blank" state, i.e. not yet having been assigned an address. The cable operators, however, are required to uncrate the converters, take them out of the boxes, remove the converter covers, remove the memory IC's in the converters, insert the IC in an independent test fixture and program a digital code into the IC. This can impose significant labor costs. In such instances, the cable operator must choose the code or address and maintain a record of the addresses applied to each converter. The application of the addresses by the cable operators raises the possibility of damage to the IC and/or the otherwise operable converter itself. With the latter approach, the cable operator is required to maintain very up-to-date and accurate records of the assigned address so that the correlation between a given address and a converter can be checked or verified and that duplicate address assignments do not occur.
Furthermore, with existing converters, the accessing of the memory to verify data in memory essentially requires the same aforementioned process used by cable operators to initially imprint the address. Again, the process is time consuming and costly and raises the possibility of damage to the unit.
It is also known to link two or more converters, one of which is called the "master" and the others are called "slaves". This master-slave capability is required to combat a form of piracy prevalent in the CATV industry.
When a subscriber has more than one converter installed in a single household, CATV operators typically charge lower rates for the additional converters as compared to the charge for the first converter installed. This pricing structure provides opportunity for theft of service in the following way. Two neighbors obtain converters and subscribe to service from a local CATV operation. The first neighbor obtains one converter with basic service and pays a nominal monthly fee. The second neighbor obtains two converters, both with full service. Although the second neighbor pays the normal full-service charge for the first converter, a much lower rate is charged for the second converter. The second neighbor then gives one of his converters to the first neighbor and both neighbors share the total monthly charge. Depending on the pricing structure of the cable system, the two neighbors may be paying a total monthly bill which is significantly lower than if both neighbors legitimately subscribed to full service.
By establishing a master-slave converter capability, multiple converters within a single household can be connected together via a hard-wire link. If the master converter is removed from the household, none of the remaining slave converters will receive enabling signals from the master and eventually become inoperable. If any slave converter is removed, it also will not receive enabling signals from its master and become inoperable in its new location.
Converters which have provided a master-slave capability have been specially designed for that purpose and have in the past, been hard-wired to each other.